1. Field of the Invention
The present invention relates to an on-vehicle camera image playback device and a car navigation device for receiving a video image (a still image or a moving image), which is to be viewed by a driver in a vehicle, from a network camera (a Web camera) for playback.
2. Description of the Background Art
In recent years, more and more people view video images, which are captured by a network camera, using a device (e.g., a PC and a mobile phone) capable of playing back a camera image at remote locations via the Internet for various purposes, for example, as a surveillance camera.
For example, in a conventional technique shown in FIG. 14, a network camera 511 placed in a house (home) is connected to an Internet network via an ADSL (Asymmetric Digital Subscriber Line) modem 513 and a broadband router 512 in a broadband environment such as an ADSL. The network camera 511 has a camera section (not shown) for capturing video images, and a digital processing section (not shown) which performs a digital process for the captured video images, and transmits the processed video images to a network side. By specifying an IP (Internet Protocol) address of the network camera 511, a mobile phone 514 and a PC 515 at remote locations are able to display video images captured by the network camera 511 using a browser, as long as the mobile phone 514 and the PC 515 are connected to the Internet wherever they are. The IP address is assigned by an Internet provider. As a result, the network camera 511 can be used as a surveillance camera. Also, the network camera 511 may be placed both inside and outside a building, whereby the goings-on within a house can be monitored, a lecture or a lesson can be distributed, parents are allowed to view what their child is doing in kindergarten or a child-care center, or a landscape of a leisure venue or traffic jam information, etc., can be viewed. The number of network cameras used for the above-described purposes is increasing, and therefore, more and more people will view the video images captured by the network camera in a vehicle.
As a combination of the above-described network camera and a sensor for detecting an emergency such as a break-in, fire, or gas leak, for example, there exists a portable security system disclosed in Japanese Patent Laid-Open Publication No. 2000-36088. In this portable security system, as shown in FIG. 15, a user, who is a resident of a house, has a mobile phone 615 as a portable information device. When a sensor 613 detects an emergency, the user away from home is notified of detection of the emergency by means of the mobile phone 615 via a wireless transceiver 612 (see arrows 1a and 1b). The user uses the mobile phone 615 to operate a camera with a microphone 611 (see arrows 2a and 2b) via the wireless transceiver 612, and receives video and audio from the camera with the microphone 611 for playback, thereby viewing what is going on in his/her house (see arrows 2c and 2d). If something goes wrong in the house, the user can control a security alarm 614 so as to be activated by using the mobile phone 615 (see arrows 3a and 3b). Also, the user can stop the security alarm 614 when the emergency is over. Alternatively, after the wireless transceiver 612 receives a signal from the sensor 613, the security alarm 614 can be activated (without the user's operation) immediately after the signal is transmitted thereto (see arrow 1c).
With the above-described portable security system using a conventional technique, when something goes wrong in the house, the user can handle the emergency by himself/herself by operating the mobile phone without relying on a security company. Also, in order to view what is going on in the house, the user can use the mobile phone 615 as a remote controller for the camera with the microphone 611 while checking video and audio, thereby remotely operating an orientation or a magnifying power of the camera (as for a method of controlling the camera using the mobile phone, also see Japanese Patent Laid-Open Publication No. 2002-57935).
However, the above-described conventional techniques are not designed to be used in a vehicle.
On the other hand, there exist an on-vehicle video mail storage/playback device and a car navigation device disclosed in Japanese Patent Laid-Open Publication No. 2002-107158, for example, which are designed to be used in a vehicle. FIG. 16 is a block diagram showing a car navigation device 71 capable of storing and playing back video mail, which is disclosed in Japanese Patent Laid-Open Publication No. 2002-107158.
In FIG. 16, a GPS receiver 723 is able to detect a current position of a vehicle on which it is mounted, a vehicle speed sensor 724 is able to detect a vehicle speed, and a G sensor 725 is able to detect acceleration exerted on the vehicle. Also, a signal processing device 716 processes input signals from the GPS receiver 723, the vehicle speed sensor 724, and the G sensor 725, and outputs a current position signal, a vehicle speed signal, and an acceleration signal. A memory 713 stores moving image data read from video mail to be transmitted/received, or from an external recording medium 721. A moving image data reading section 715 reads moving image data from the external recording medium 721 (for example, a memory card). A communication control section 712 is an interface for controlling a mobile phone 72 to establish exchange of communication data. A rendering LSI 714 is a circuit for converting video mail to be transmitted/received to rendering data, thereby causing a display monitor 720, which is placed inside the vehicle, to display the video mail. Note that the display monitor 720 is placed on a vehicle dashboard near a driver. A current position calculating section 718, which is connected to a CPU 711, calculates a current position based on the current position signal from the GPS receiver 723, and a route search section 719 searches for an optimal route from the calculated current position to a destination point or an intermediate point, which is input by the user. The current position calculating section 718 and the route search section 719 are realized by a program. A DVD-ROM drive 717 is a cartographic data reading section for reading cartographic data from a DVD-ROM 722 in which the cartographic data is stored.
In the car navigation device 71 structured as described above, the CPU 711 determines whether or not the vehicle is stopped based on the vehicle speed signal from the vehicle speed sensor 724 or the acceleration signal from the G sensor 725. The CPU 711 causes the display monitor 720 to display the received video mail after reading it from the memory 713 only when the CPU 711 determines that the vehicle is stopped. As such, the received video mail is not displayed while the vehicle is traveling in order to prevent the driver from losing concentration while driving, thereby ensuring safety.
The techniques disclosed in Japanese Patent Laid-Open Publication No. 2000-36088 and Japanese Patent Laid-Open Publication No. 2002-57935 undeniably present a safety hazard because the user has to operate buttons of a portable device (e.g., a mobile phone or a PHS) while watching a small display monitor thereof at frequent intervals in order to view camera images and adjust an orientation of the camera, thereby being prevented from concentrating on driving. Thus, it is necessary to revise the above-described techniques so that the driver can use them in the vehicle safely and conveniently.
On the other hand, the car navigation device disclosed in Japanese Patent Laid-Open Publication No. 2002-107158, whose target user is a driver in the vehicle, performs playback of video mail only when the vehicle is stopped for safety's sake. As a result, the user is not allowed to view the video mail for checking the content thereof in the traveling vehicle. This does not really matter in the case of video mail which often includes less urgent information. However, it is a significant disadvantage if the user is not allowed to view information which is important or urgent while he/she is driving. For example, in the case where video data of a network camera used for the purpose of security is received, the user has to check a video image of the video data in real time. However, the user is not allowed to check it in real time while he/she is driving a vehicle. As a result, this is a real disadvantage if the user has to drive for a long time without a stop (e.g., the user has to drive for a long time until the next stop when he/she travels along an expressway).
Thus, there is a need for an on-vehicle network camera image playback device which is capable of solving a problem of a trade-off between safety and convenience.